Refining photoconductive particle

ABSTRACT

Apparatus for refining composite photoconductive particles comprising transparent cores with photoconductive films disposed thereon, the apparatus comprising means for uniformly charging and dispersing the composite particles in a layer on an electroconductive member so that the composite particles are electrostatically attracted to the electroconductive member, means for uniformly exposing the layer of composite particles to radiation within the sensitive wavelength region thereof to reduce the electrostatic attraction of desired composite particles for the electroconductive member, and first removing means for removing the desired composite particles from the electroconductive member.

United States Patent [1 Tamai et al.

[ REFINING PHOTOCONDUCTIVE PARTICLE [75] Inventors: Yasuo'Tamai, Asaka;Shigeru Sadamatsu, Odawara, both of Japan 73 Assignee: Fuji Photo FilmCo., Ltd.,

Kanagawa, Japan 22 Filed: Dec. 2,1971 21 Appl. No.: 204,055

[30] Foreign Application Priority Data Dec. 2, 1970 Japan 45-106638 [52]US. Cl 209/127 R [51] Int. Cl. B03c 7/08 [58] Field of Search 209/127 R,128, 129,131; 15/15 [56] References Cited UNITED STATES PATENTS2,924,519 2/1960 Bertelsen 1l7/17.5 1,354,063 9/1920 Payne 1. 209/1313,308,948

3/1967 Barthelemy 209/127 R Mar. 26, 1974 Breakiron et al. 209/127 RRobinson 209/129 Primary Examiner-Tim R. Miles Assistant Examiner-RalphJ. Hill Attorney, Agent, or Firm-Gerald J. Ferguson, Jr.

[ 5 7 ABSTRACT Apparatus for refining composite photoconductiveparticles comprising transparent cores with photoconductive filmsdisposed thereon, the apparatus comprising means for uniformly chargingand dispersing the composite particles in a layer on anelectroconductive member so that the composite particles areelectrostatically attracted to the electroconductive member, means foruniformly exposing the layer of composite particles to radiation withinthe sensitive wavelength region thereof to reduce the electrostaticattraction of desired composite particles for the electroconductivemember, and first removing means for removing the desired compositeparticles from the electroconductive member.

7 Claims, 5 Drawing Figures PAIENTEDIARZB I974 FIG. 2

FIG. I

FIG. 4

REFINING PHOTOCONDUCTIVE PARTICLE BRIEF DESCRIPTION OF THE DRAWING FIGS.1 to" 4 are the cross-sectional views of photoconductive particles ofdifferent shapes.

FIG. 5 is a cross-sectional side view of a device embodying thisinvention.

DETAILED DESCRIPTION OF THE INVENTION This invention relates to animprovement in electrophotographic process, and particularly to aprocess for refining photoconductive particles;

One of the electrophotographic process already known utilizes thecombination of photoconductive particles and electroconductive plate asdisclosed for example in Japanese Patent Publication No. 12385/69 and8838/70. Said process consists of the steps of either scattering thephotoconductive particles to form a layer thereof on anelectroconductive material and then electrostatically charging thusformed layer or dispersing photoconductive particles previously chargedon said material to form a layer of said particles, then subjecting saidlayer to imagewise exposure, removing the particles of whichelectrostatic charge is dissipated by said exposure and fixing theremaining particles thereon or after transferring to other suitablematerials.

The invention relates to the refining process of the photoconductiveparticles of the above mentioned type after the manufacture thereofand/or after the repetitive use thereof.

The photoconductive particles for use in electrophotographic process ofthe above-mentioned type contain core materials. In this invention, thecore materials should be considerable transparent (absorptioncoefficient not exceeding l.3 X mm") to the radiation of the major partof sensitive wavelength region of the photoconductive materials used insaid process.

Said core material can be composed of glass, thermoplastic resin,solvent soluble resin, metal oxide, etc. Also said photoconductivematerial can be those oridinarily employed in-the electrophotographicprocess of the above mentioned type, such as selenium, cadmium sulfide,zinc sulfide, anthracene, zinc oxide etc., orthe mixture thereof withinsulating resin.

- FIG. 1 shows the enlarged cross section of photoconductive particlespreferred for use in the electrophotographic process of theabove-mentioned type. In FIG. 1, a transparent core 11 is uniformlycovered with an insulating photoconductive layer 12. Such particles asshown in FIG. 1 stick to an electroconductive plate by electrostaticattractive force when electrostatically chargedin a dark place, andefficiently lose the electrostatic charge thereon when exposed to lightand becomes removable from said electroconductive plate.

FIG. 2 shows the enlarged cross-section of photoconductive particlesformed in the course of manufacture of said particles and provided withunpreferable shape. Such particlesdo' not contain transparent corematerial therein but consist exclusively of insulating photoconductivematerial 13. Such particles as shown in FIG. 2 also stick to anelectroconductive plate by electrostatic attractive force whenelectrostatically charged in a dark place, but do not easily lose theelectrostatic charge even when exposed to light and thus remainunremovable on said plate. That is to say, such particles 1 are providedwith far lower sensitivity to light compared with the particles as shownin FIG. 1, and the presenceof the unpreferred particles in those asshown in FIG. 1 gives rise to elevated fog level.

FIG. 3 shows the enlarged cross-section of particles of alsounpreferable shape. In this case the core material 11 is notsufficiently covered with insulating photoconductive material 12. Suchparticles are formed either in the manufacturing process thereof or inthe repeated use thereof in the electrophotographic process of theabove-mentioned type. When the core material 11 is composed of asubstance provided with electric insulating materials such as plasticsor glass, such particles do not easily lose the electrostatic chargethereon even under light exposure becausesaid core material 11 isexposed on the surface as shown by 14, 14' and 14", and therefore becomedifficultly removable. Consequently, such particles also lead tofogging.

FIG. 4 shows the enlarged cross-section of photoconductive particles ofalso unsatisfactory performance. In this case the core material 11 iscompletely covered with the insulating photoconductive layer 12, but thesurface thereof is contaminated with material of low electric resistance21, 21 and 21". Such particles show significantly lowered chargeretaining ability, and therefore cannot be deposited on anelectroconductive plate by means of charging operation in a dark place.Consequently, an electrophotographic process of the above-mentioned typecarried out with photoconductive particles containing such particleswillonly provide defective reproductions.

The object of this invention is to provide a process for eliminating theparticles of unsatisfactory or unpreferred property as shown in FIGS. 2to 4 from the photoconductive particles to obtain particles of desirableperformance.

This invention enables not only to remove the particles of undesirableproperties as shown in FIGS. 2 to .4 formed in the course ofmanufacturing photoconductive particle, but also to remove the particlesof undesirable properties formed by the repetitive use of saidphotoconductive particles. Besides the process of this invention enablesto remove insulating or electroconductive alien particles dust duringthe repetitive use of photoconductive particles.

More specificially this invention is to provide a process for refiningthe photoconductive particles containing core material beingconsiderably transparent (absorption coefficient not exceeding 1.3 X 10mm") to the radiation of major portion of sensitive wavelength range ofthe photoconductive material employed thereon, which comprises eitherdusting said particles on a electroconductive plate andelectrostatically charging the layer thus formedof said particles ordusting said particles electrostatically charged in advance on saidplate, then mechanically removing the particles provided withweakerelectrostatic attractive force, exposing said layer of particlesuniformly to a radiation within the sensitive wavelength range therebydissipating the sticking force of photoconductive particles to saidelectroconductive plate and finally collecting the remaining particleson said plate, thereby to fractionate the particles according to thechange of sticking force thereof before and after the exposure toradiation.

More'practically the change of sticking force of the photoconductiveparticles to the electroconductive plate is utilized as follows:

I. The particles contained in the particle layer but not chargeable areremoved by utilizing the reduced sticking force thereof to theelectroconductive plate. It is therefore made possible to eliminate theparticles of significantly low charge retaining ability as shown in FIG.4 or electroconductive or low-resistance dust mixed in the particlesduring the course of repetitive use thereof. Practically this operationis realized by inclining the plate holding charged particle layerthereon thereby removing the undesirable particles and dust by gravityand/or blowing air stream to said particle layer to remove suchundesirable particles and dust.

II. The satisfactory photoconductive particles as shown in FIG. 1 arecollected by exposing said particles to radiation thereby dissipatingthe sticking force thereof to the electroconductive plate. It is thusmade possible to collect the particles adapted for use in theelectrophotographic process utilizing the photoconductive particles ofthe above-mentioned type. The particles sticking on theelectroconductive plate lose the electrostatic attractive forcethereof'by uniform exposure to light and then are collected by gravity,air stream or suitable vibration.

The defective particles as shown in FIGS. 2 and 3 which do not lose theelectrostatic charge thereof by the radiation still stick on saidelectroconductive plate. Thus, the photoconductive particles of lowersensitivity or having exposed core material and insulating dust mixed inthe course of repetitive use remain on the electroconductive plate. Suchremaining particles are removed from said electroconductive plate bymechanical removing such as with brush and/or blowing of strong airstream. Such operation can be combined with the steps of dissipating thecharge on such particles such as corona discharged, blowing of ionizedgas stream, radiation, etc.

From practical point of view, the electroconductive plate is preferablyused repeatedly, and thereby conveniently formed into an endless belt.Such electroconductive plate can be composed of metal plate,electroconductive rubber, metal plate lined with flexible material, etc.

The device for embodying this invention will be explained in referenceto attached FIG. 5.

The container 31 contains photoconductive particles 32 freshlymanufactured or containing undesirable particles as the result ofrepetitive use thereof. Said photoconductive particles 32 are scooped upby the roller 33 from the bottom of said container 31 and are made tofall.

Uniform distribution is realized by the air stream from the dust 34,which is blown from a slit 36 provided on a cushioning box 35 to thefalling particles. Said falling particles are electrostatically chargedby the corona discharge generated by a corona electrode 37, thereby toform a charged particle layer 39 on an electroconductive belt 38, whichis driven by the driving rollers 40, 41 and 42. Also provided are therollers 43 which are in contact with the both side portions of saidbelt. Contaminated particles as shown in FIG. 4 and electronconductiveor low resistance dust contained in the particle layer are removedtherefrom by the air stream supplied from a duct 44 and collected in acontainer 45 of reduced pressure. The electroconductive particles thuscollected are shown by 46.

Then the particle layer on the endless belt is exposed to lightuniformly by a light source 48 located in the lamphouse 47. Thephotoconductive particle lose the sticking force and fall apart from thebelt 38 by the gravity or by the air stream from the duct 50, thenbrought into a container 49 of reduced pressure and finally collected bya cyclon etc.

The particles retaining electrostatic charge still after said exposureand insulating dust, which are still remaining on the electroconductiveplate 38, are wiped off and removed by a brush 52 provided in a casing51 of reduced pressure. Thus it is made possible to remove theundesirable particles and dust contained in the photoconductiveparticles.

The refining process according to this invention is applicable both forrefining the photoconductive particles after the manufacture thereof andfor restoring the performance of the photoconductive particles afterrepetitive use thereof.

This invention, therefore, enables not only to dispense with the specialclassification process thus far required after the manufacture ofphotoconductive particles but also to prolongate the lifetime of thephotoconductive particles, and thus have an elevated industrial value.

What is claimed is:

l. A process for refining photoconductive particles for use inelectrophotographic process and containing core material havingan-absorption coefficient not exceeding 1.3 X 10 mm to the radiation ofthe major part of the sensitivity wavelength range of thephotoconductive material employed thereon, which comprises eitherdusting said particles on an electroconductive plate andelectrostatically charging thus formed particle layer or dusting saidparticles electrostatically charged in advance on said plate to form alayer thereon, mechanically removing particles scarcely charged byutilizing the reduced sticking force thereof to said electroconductiveplate, then exposing said particles layer uniformly to light coveringwhole sensitive wavelength range or a part thereof thereby dissipatingthe sticking force of said particles to said plate, and finallycollecting said photoconductive particles.

2. Apparatus for refining composite photoconductive particles comprisingtransparent cores with photoconductive films disposed thereon, saidapparatus comprising:

means for uniformly charging and dispersing said composite particles ina layer on an electroconductive member so that said composite particlesare electrostatically attracted to said electroconductive member;

means for uniformly illuminating all of said layer of compositeparticles to radiation within the sensitive wavelength region thereof toreduce the electrostatic attraction of desired composite particles forsaid electroconductive member with respect to that of undesiredcomposite particles so that said desired particles are differentiatedfrom said undesired particles in accordance with their respectiveelectrostatic attractions for said electroconductive member after theyhave both been subjected to said uniform illumination step; and firstremoving means for selectively removing said desired composite particlesfrom said electroconductive member. 3. Apparatus for refining compositephotoconductive particles comprising transparent cores withphotoconductive films disposed thereon, said apparatus comprising:

means for uniformly charging and dispersing said composite particles ina layer on an electroconductive endless belt so that said compositeparticles are electrostatically attracted to said electroconductiveendless belt; means for uniformly exposing said layer of compositeparticles to radiation within the sensitive wavelength region thereof toreduce the electrostatic attraction of desired composite particles forsaid electroconductive endless belt; and first removing means forremoving said desired composite particles from said electroconductiveendless belt; I

second removing means for removing the undesired composite particlesremaining on said electroconductive endless belt after said desiredcomposite particles have been removed therefrom and before the compositeparticles are dispersed thereon, said undesired particles exhibitingsubstantially more electrostatic attraction for said electroconductiveendless belt than said desired particles.

4. Apparatus as in claim 3 where said second removing means comprises abrush disposed within a chamber maintained at reduced pressure.

5. Apparatus as in claim 3 where said first removing means comprises acontainer so disposed with respect to said endless belt that saiddesired composite particles fall because of gravity into said container.

6. Apparatus for refining composite photoconductive particles comprisingtransparent cores with photoconductive films disposed thereon, saidapparatus comprising:

means f0 uniformly charging and dispersing said composite particles in alayer on an electroconductive member so that said composite particlesare electrostatically attracted to said electroconductive member;

means for uniformly exposing said layer of composite particles toradiation within the sensitive wavelength region thereof to reduce theelectrostatic attraction of desired composite particles for saidelectroconductive member; and

first removing means for removing said desird composite particles fromsaid electroconductive member;

third removing means for removing further undesired composite particlesbefore said first removing means removes said desired compositeparticles, said further undesired particles exhibiting substantiallyless'electrostatic attraction for said electronconductive member thansaid desired particles.

7. Apparatus as in claim 6 where said third removing means comprisesmeans for blowing a jet of air onto said layer of composite particles toloosen said further undesired particles from said electroconductivemember.

1. A process for refining photoconductive particles for use inelectrophotographic process and containing core material having anabsorption coefficient not exceeding 1.3 X 102mm 1 to the radiation ofthe major part of the sensitivity wavelength range of thephotoconductive material employed thereon, which comprises eitherdusting said particles on an electroconductive plate andelectrostatically charging thus formed particle layer or dusting saidparticles electrostatically charged in advance on said plate to form alayer thereon, mechanically removing particles scarcely charged byutilizing the reduced sticking force thereof to said electroconductiveplate, then exposing said particles layer uniformly to light coveringwhole sensitive wavelength range or a part thereof thereby dissipatingthe sticking force of said particles to said plate, and finallycollecting said photoconductive particles.
 2. Apparatus for refiningcomposite photoconductive particles comprising transparent cores withphotoconductive films disposed thereon, said apparatus comprising: meansfor uniformly charging and dispersing said composite particles in alayer on an electroconductive member so that said composite particlesare electrostatically attracted to said electroconductive member; meansfor uniformly illuminating all of said layer of composite particles toradiation within the sensitive wavelength region thereof to reduce theelectrostatic attraction of desired composite particles for saidelectroconductive member with respect to that of undesired compositeparticles so that said desired particles are differentiated from saidundesired particles in accordance with their respective electrostaticattractions for said electroconductive member after they have both beensubjected to said uniform illumination step; and first removing meansfor selectively removing said desired composite particles from saidelectroconductive member.
 3. Apparatus for refining compositephotoconductive particles comprising transparent cores withphotoconductive films disposed thereon, said apparatus comprising: meansfor uniformly charging and dispersing said composite particles in alayer on an electroconductive endless belt so that said compositeparticles are electrostatically attracted to said electroconductiveendless belt; means for uniformly exposing said layer of compositeparticles to radiation within the sensitive wavelength region thereof toreduce the electrostatic attraction of desired composite particles forsaid electroconductive endless belt; and first removing means forremoving said desired composite particles from said electroconductiveendless belt; second removing means for removing the undesired compositeparticles remaining on said electroconductive endless belt after saiddesired composite particles have been removed therefrom and before thecomposite particles are dispersed thereon, said undesired particlesexhibiting substantially more electrostatic attraction for saidelectroconductive endless belt than said desired particles.
 4. Apparatusas in claim 3 where said second removing means comprises a brushdisposed within a chamber maintained at reduced pressure.
 5. Apparatusas in claim 3 where saiD first removing means comprises a container sodisposed with respect to said endless belt that said desired compositeparticles fall because of gravity into said container.
 6. Apparatus forrefining composite photoconductive particles comprising transparentcores with photoconductive films disposed thereon, said apparatuscomprising: means fo uniformly charging and dispersing said compositeparticles in a layer on an electroconductive member so that saidcomposite particles are electrostatically attracted to saidelectroconductive member; means for uniformly exposing said layer ofcomposite particles to radiation within the sensitive wavelength regionthereof to reduce the electrostatic attraction of desired compositeparticles for said electroconductive member; and first removing meansfor removing said desird composite particles from said electroconductivemember; third removing means for removing further undesired compositeparticles before said first removing means removes said desiredcomposite particles, said further undesired particles exhibitingsubstantially less electrostatic attraction for said electronconductivemember than said desired particles.
 7. Apparatus as in claim 6 wheresaid third removing means comprises means for blowing a jet of air ontosaid layer of composite particles to loosen said further undesiredparticles from said electroconductive member.